Hose connections for pilot control lines are used for example, to control construction machines exposed to severe operating conditions. This is especially true for underground building operations, because the operating conditions prevailing therein pose the highest requirements. For example, when control installations or working machines change their locations, it is necessary to interrupt existing hose connections, wherein plug couplers are used.
Pilot control lines, in particular, have very small cross sections with diameters, for example, of 1.8 mm, whereby the hydraulic medium is exposed to pressures of, for example, 500 bar. The plug pins of the fittings of the pilot control lines are, therefore, extremely sensitive and in order to obtain secure plug contacts, the sealing elements are subject to very high requirements. Furthermore, it is necessary to couple simultaneously a large number of pilot control lines, so that their location in the socket piece and the arrangement and dimensioning of the bores in the socket piece must be effected with the utmost accuracy and simple and rapid coupling without damaging the plug pins and particularly, their seals must be assured.
It is further necessary to provide simple measures for the rapid and safe replacement of sealing elements.
In order to solve the problem of the ready installation and dismantling of the seals, it is known to manufacture a socket piece in two parts, i.e., a structural base part equipped with bores and a plate provided with corresponding bores, this plate being bolted to the base part. The bores of the base part are provided with grooves so that they are readily accessible for the installation of seals when the plate is released.
The manufacturing basis for the tolerances of the pitch circle bores is DIN (Deutsche Industrie Norm: German Industrial Standard) 7168, which yields a sealing gap in the radial direction of 0.8 mm, with an assumed bore diameter of 3.4 mm.
Such a sealing gap is unsuited for important applications of plug couplers, because under the pressure being applied, the seals are driven into the gap and thus destroyed. Similarly, in the coupling process, the misalignment of the bores between the plate and the base part leads to the rapid destruction of the seals.
To reduce such manufacturing tolerances, it is further known to clamp together the base part with the plate during the production of the correctly aligned bores by means of locating pins and then to drill the bores together. In order to clamp the parts together and to safely secure them against each other, it is necessary, however, to overdimension the locating pins, so that they can no longer be separated without special auxiliary means. This, in turn, is in contradiction to the requirement of the rapid and simple replacement of seals.
In order to prevent the destruction of seals and to reduce wear during the plugging process, it is further necessary to avoid damage to the plug-in pins of the nose fittings during the insertion process, because the grooves being formed may injure the seals, so that at the high pressures required, the plug coupling may become unusable.